Field of the Invention
The present invention relates to a randomly piled parts pick-up apparatus that takes out a part with a robot, and to a control method for the apparatus.
Description of the Related Art
A randomly piled parts pick-up apparatus is an apparatus that recognizes a position and an orientation of each individual part (hereinafter, referred to as workpieces) from parts and the like that are randomly piled in an overlapping manner, and takes out the workpieces one by one with a robot. An operation of taking out a workpiece is hereinafter, referred to as “pick-up operation”.
The randomly piled parts pick-up apparatus mainly includes a three-dimensional shape measurement device and a pick-up robot. Base on distance information obtained by the three-dimensional shape measurement device, the randomly piled parts pick-up apparatus recognizes the position and the orientation of a workpiece that can be grasped, and notifies the pick-up robot of the position and the orientation. The pick-up robot picks up the workpiece from the randomly piled parts based on the information on the position and the orientation thus notified. The randomly piled parts pick-up apparatus needs to complete a cycle of a series of operations, including an operation of measuring a three-dimensional shape of the randomly piled parts, an operation of recognizing and notifying the position and the orientation of a workpiece, and an operation of picking up the workpiece, in a short period of time.
Some randomly piled parts pick-up apparatuses include a camera that captures a scene indicating a state of randomly piled workpieces, in addition to the three-dimensional measurement device, and achieves a pick-up cycle completed in a shorter period of time in the following manner. More specifically, after the pick-up operation is performed and before the three dimensional measurement of randomly piled parts is performed again, a two-dimensional image that represents the state of the randomly piled parts and is captured by the camera is acquired. Then, this two-dimensional image is compared with a two-dimensional image that represents the scene of the randomly piled workpieces and is captured after the pick-up operation in the previous cycle. Thus, whether there is a workpiece with no change in the position and the orientation exceeding an allowable range is determined. When there is the workpiece with no change exceeding the allowable range, the workpiece is picked up with no three-dimensional measurement performed.
However, the method discussed in Japanese Patent Application Laid-Open No. 2010-120141 has an issue in that changes in a height direction cannot be detected because the detection of changes in the position and orientation of the workpiece depends on two-dimensional images.